This quest is incredibly hard for the level it's at. Swarms of enemies and tougher spawns that have 10 ab plus sneak attack. I just ran it with a level 4 fighter with protection from evil, bull's, and magic weapon all up and we wiped. Two of the armors attacked him flanked by two summon monster II fire's and it massacred us and the elementals with no effort..
This quest really feels like it's meant for at least 6, but probably 7.
Yup, definitely a tough quest... The trend usually is for people to reach lvl 6 around Sanctuary so its easily missed.
I would like this to be a lvl 7 quest as well, with decent XP if you complete it at lvl 6 or under. (Actually if I recall correctly the XP was pretty worth the risk anyway) The boss and the stronger variant of minion in there are quite tough cookies.
Its one of those quests where one ends up having at least one person consistently using up purple crystals, or a fair few blurs for the party used up..